As the worldwide demand for gasoline and other light refinery products has steadily increased, there has been a significant trend toward conversion of higher boiling compounds to lower boiling ones. To meet the increasing demand for distillate fuels increased, refiners have investigated various reactors, such as hydrocracking reactors, residual desulfurization units (RDS), and solvent deasphalting (SDA) units, to convert Residuum, Vacuum Gas Oil (VGO) and other heavy petroleum feedstocks to jet and diesel fuels.
Catalysts have been developed that exhibited excellent distillate selectivity, reasonable conversion activity and stability for heavier feedstocks. The conversion rates attainable by the various processes are limited, however. For example, RDS units alone can produce a 1 wt % sulfur fuel from high sulfur residua, but conversions are generally limited to about 35% to 40%. Others have proposed to use SDA units to solvent deasphalt the residuum feed and process the deasphalted oil only in a Residuum Hydrocracking Unit (RHU). Also, others have processed the unconverted vacuum residuum from a RHU in an SDA unit and recycled the deasphalted oil (DAO) back to the front end of the RHU. Still others have proposed to process the SDA pitch directly in a RHU. Nonetheless, economic processes to achieve high hydrocarbon conversions and sulfur removal are desired.